The present invention relates to an internal combustion engine, such as a gasoline engine for an automobile, having an electronically-controlled fuel injection system, and particularly to a fuel dispensing device for an internal combustion engine including fuel injection valves with associated atomizers.
Recent advanced electronics in the automobile industry has involved the engine components, and several control techniques such as electronic advancer control and electronic fuel injection control have been put into practice. Particularly, the introduction of microcomputer into the control circuit has brought a further sophisticated control to the fueling system and combustion system of the engine.
However, electronic fuel injection systems available currently are still inferior in some properties to the conventional carburetor fueling systems, and they are still incomplete in the matter of cost and reliability. Possible approaches to the cost reduction of the electronic fuel injection system are a smaller number of injection valves, a lower fuel supply pressure to the injection valve, and a smaller capacity of the fuel pump. When the number of injection valves is reduced, each injection valve needs to feed more than one cylinder. However, because of uneven and relatively large fuel particles fed by the injection valve, it is difficult to fuel more than one cylinder evenly with one injection valve, and this causes a fall in the exhaust emission purify efficiency and fuel combustion efficiency, resulting in a rise in the fuel consumption and the toxic level of exhaust emission.
In order to fuel all cylinders evenly, the entry section of the intake manifold needs to be narrowed to form a collective room, but with the result of an increased manifold resistance, which hampers the upgrading of the engine output power.
For fueling all cylinders evenly with a reduced number of injection valves, there is known a method of making fine fuel particles using an ultrasonic device called "atomizer", as disclosed for example in U.S. Pat Nos. 2,949,900 and 4,106,459. This system is intended to fuel a plurality of cylinders by conducting the fuel injected with a single injector through an atomizer, allowing the even fuel distribution to all cylinders and the improvement in the performance of the engine. However, because of a single injection valve, this conventional system is not fairly applicable to high-power oriented engines and has a problem of being lacking in reliability against the failure of the injection valve.
The shortcomings of the single injection valve system naturally lead to a system using two or more injection valves, but smaller in number than the number of cylinders, i.e., applicable to engines having at least four cylinders. This modified scheme, however, needs an increased number of atomizers to match the number of cylinders, impairing the cost reduction intended by use of a smaller number of injection valves.